I'm so confused and don't want to get bad again...

So life has been great lately. I got engaged to my best friend and soul mate. I have a good job. But my insomnia has been really bad lately and my mind won't shut up and let me sleep. When I am not actively doing stuff to distract myself (and thus making my insomnia worse), I find my brain composing suicide notes or imagining ways I could commit suicide. Almost daydreaming about myself lying dead in my apartment by various means. And it scares the crap out of me. I haven't been actively suicidal in almost two years and I've been able to almost completely stop self harming in the last year, only breaking twice when emotions and stress got the better of me. But no matter how great life seems or how many encouraging tattoos I get to remind myself not to give up, my mind still wanders and torments me. And a part of me wants to give in. I don't even know if I'm staying alive for myself anymore or just because I don't want to put my fiance through finding my body. I've been so stressed lately that I actually developed a psychogenic movement disorder that put me on medical leave from work for almost a month. I've been emotional and anxious and paranoid. My fiance is doing everything he can to help me and keep me happy and healthy. Reminding me to eat (long story, basically Prozac messed something up in my brain where I am never actually hungry despite not being on it for almost 3 years). Sometimes I forget for so long that I end up fainting. But the only reason I find myself caring that I fainted is because it scares my fiance. I actually miss the numbness, the total lack of any emotion whatsoever that I used to have. I'm just lost and really need someone to talk to who understands what it's like to have depression and anxiety like this. For all he does to help me with everything, my fiance doesn't have depression or anxiety so he can't really understand what I'm going through and trying to explain it to him just makes him feel sad and helpless. I've been bottling this all up trying to protect him from it but it's to the point that when I do sleep I wake up every hour or so from nightmares of my own or my friends suicides, and I'm barely managing 4-6 hours of sleep per night without taking melatonin or benadryl. At least with those I don't dream. I have gotten to the point where I am afraid to sleep and will do almost anything to avoid it. I've exhausted all the coping mechanisms that I learned in the hospital after my first attempt. No matter what I try to tell myself about how good life is and how I need to keep going because it's great and worth living, how people love me, etc... I can't quite bring myself to really believe it when I say it. To be bluntly honest my anxiety has made me distrust everyone, even my closest friends, whispering that they actually hate me but are just politely tolerating me hoping that I leave them alone. This anxiety is only reinforced by my two closest friends suddenly turning their backs on me within the past 6 months and blocking me on every social media platform and phone number. I wish I could shrug it off and say their loss and I don't need friends like them but to be honest they were pretty much the only people I really really trusted to be myself around (except my fiance). It's never been easy for me to make friends in real life because I'm either really awkward and shy or over the top bubbly and optimistic around people I don't really know and both seem to push everyone away. I'm just feeling so lost and alone and forgotten, even though rationally I know that I am not alone and certainly not forgotten. Anxiety and depression are the little Devils on my shoulders and it feels like they killed the little angel hope over 10 years ago when I first started feeling like I wanted to end it all and started hurting myself to deal with my emotions. So yeah I kinda tend to ramble a lot, but it's so much easier for me to write or type something emotionally charged like this. I don't know if I could ever actually express these thoughts out loud, even I'd I was reading what I have written here. So yeah... advice?

I'm so sorry you're going through this alone! It's difficult explaining depression and anxiety to a person who doesn't struggle with it daily. I'm sorry your fiance cannot fully understand how you're feeling. Have you talked to a therapist or counselor? Maybe that person can give you new coping mechanisms? The only ones I know about for anxiety are to clear your mind by thinking "dark, dark, dark" until your mind is clear. It takes A LOT of practice but helps occasionally. The other is to make your muscles tense, and then release that tension. That way your body gets some of your energy out. You're supposed to focus on one muscle group at a time and kinda work your way down your body.
As far as being anxious during the day, if you're standing, then sit down and do something and if you're sitting down and anxious, get up and be active. I was always told to change your situation when your anxiety gets bad.
I just read something about getting better sleep and I guess sometimes vitamins will help: Melatonin, Vitamin D and Magnesium. I haven't had much success with it, but maybe it will help you!
I really think you should open up more to your fiance. He may not understand but I think you will feel better after you tell someone how you're feeling.
I hope things look up for you soon! Hang in there!